What is Paradox: Definition and 1000 Discussions

A paradox is a logically self-contradictory statement or a statement that runs contrary to one's expectation. It is a statement that, despite apparently valid reasoning from true premises, leads to a seemingly self-contradictory or a logically unacceptable conclusion. A paradox usually involves contradictory-yet-interrelated elements that exist simultaneously and persist over time.In logic, many paradoxes exist which are known to be invalid arguments, but which are nevertheless valuable in promoting critical thinking, while other paradoxes have revealed errors in definitions which were assumed to be rigorous, and have caused axioms of mathematics and logic to be re-examined. One example is Russell's paradox, which questions whether a "list of all lists that do not contain themselves" would include itself, and showed that attempts to found set theory on the identification of sets with properties or predicates were flawed. Others, such as Curry's paradox, cannot be easily resolved by making foundational changes in a logical system.Examples outside logic include the ship of Theseus from philosophy, a paradox which questions whether a ship repaired over time by replacing each and all of its wooden parts, one at a time, would remain the same ship. Paradoxes can also take the form of images or other media. For example, M.C. Escher featured perspective-based paradoxes in many of his drawings, with walls that are regarded as floors from other points of view, and staircases that appear to climb endlessly.In common usage, the word "paradox" often refers to statements that are ironic or unexpected, such as "the paradox that standing is more tiring than walking".

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  1. J

    I The Twin Paradox implies that the Universe as a whole is a special frame

    The Twin Paradox implies that the universe as a whole is a special frame of motion according to "Relativity Simply Explained" by Martin Gardner. I want to be sure than I haven't misunderstood something. I don't find the explanation completely clear. If the universe as a whole is a special and...
  2. A

    I Help Solve Twin Paradox Calc: A & B 1 Lyr Apart

    A and B 1 lyr apart and sync watches, C moving at .5 C, when at B, C sync watch with B, what time does A and C's watch show when meet. (I was told answer already here but could not find).
  3. vanhees71

    I Twin Paradox Freely Falling Observers

    Here I consider the twin paradox for two observers moving in the Schwarzschild spacetime, i.e., the spacetime where one has one radially symmetric non-rotating star, leading to the invariant line element (written in the usual Schwarzschild coordinates) $$\mathrm{d} s^2=\left (1-\frac{R}{r}...
  4. George Plousos

    I A version of the twin paradox without accelerations

    Bob is standing on Earth and Alice is on a distant planet at a constant distance from Earth. Their watches are already synchronized in the following sense: Suppose Alice's planet is a light-year away from Earth. Bob emits a light signal to Alice at time t = 0 according to Bob's watch. When Alice...
  5. Tony Wright

    B Twin paradox explained for laymen

    As a layman I also have conceptual difficulties with the twin paradox. It would allow me to move on if some one could quickly answer the rather obvious question: would there be any time dilation if the Earth was removed entirely from the thought experiment so that the twins are in a symmetrical...
  6. akashpandey

    Momentum paradox: Why can't we write it as p=m+v ?

    So as we know momentum has a formula p=mv right ? But why we can't write it as p=m+v ? The real question is why we multiply both mass and velocity quantity And not add them ?
  7. Helena Wells

    A Resolving the Paradox: Combining Quantum Mechanics and Special Relativity

    According to Bell's theorem quantum mechanics is not local.How can we combine it with Special Relativity which is local and gives us another successful theory?
  8. J

    I Detonator Paradox" Re-Cast: Can a Thin Wire Prevent a Bomb?

    In Taylor and Wheeler, problem 6-5 "Detonator Paradox," a T-shaped plunger is not long enough to strike a detonator inside a U-shaped container. However, if the T-shaped plunger is moving relativistically, then in the reference frame of the T, the U shape is shorter and so the T is able to...
  9. M

    I Twin Paradox Explained: No Math Required

    Hello I have been trying to understand the twin paradox (without math) but I’m still trying to grasp the idea. I have seen and read enough tutorials to know that acceleration is not needed for the twin paradox to be solved. For anyone who doesn’t know the twin paradox without acceleration...
  10. S

    B Double Slit Paradox: A Wave-Particle Mystery

    Let's take a pair of particles A and B that are in a quantum entanglement state, and shoot them in different directions. Along the way, one of them will pass in the famous screen of the two slits, say B. According to the known experiment, if we put a detector in one of the slits, we will lose...
  11. D

    B My argument why Hilbert's Hotel is not a veridical Paradox

    Hello there, I had another similar post, where asking for proof for Hilbert’s Hotel. After rethinking this topic, I want to show you a new example. It tries to show why that the sentence, every guest moves into the next room, hides the fact, that we don’t understand what will happen in this...
  12. S

    B Can time pass slower on another planet, causing the Twin Paradox?

    It is a long message indeed but there is one doubt I want to ask, As from the above video the time measured by the person which is outside the Frame of reference let's say t' depends on the position and time measured by the person within the Frame of reference. But how do we know that whose...
  13. W

    I Twin Paradox: Who Is Right, A or B?

    In this version of the twin paradox one twin, A, is located on earth, and the other twin, B, is located on a distant planet, which is at a fixed location in A's frame of reference. At the beginning time t = 0 the twins are stationary and their clocks are synchronized at 0. A gets on a rocket...
  14. qwereqe

    Detecting the Alignment of an Inf. Plane Capacitor: A Paradox?

    Assuming we have an infinite plane capacitor,where the upper plate is charged positively and the bottom layer is charged negatively. Now we know the field outside the capacitor is zero so we can't tell if the positive charge is on the upper plate or the lower plate. But, if we place it inside...
  15. Gjmdp

    I The Paradox of u=v | Solve the Mystery

    Let u, v be column vectors n x 1 and M a m x n matrix over a field K. If M*u= M*v, then (M^-1)*M*u=(M^-1)*M*v, thus, I*u=I*v. Hence u=v. But that shouldn't be the case. What is wrong in my reasoning? Thank you.
  16. Attu

    B Neutron Star Paradox: Understanding Coulomb & Gravitational Forces

    For instance let's take that a neutron star mass is so high that the gravitational force is more than the coulumb force. If this happens then then the electrons will go down and alpha particle will be left . This is not observed in the star so how will the particle stay normal By the way I am...
  17. G

    I Solving the Paradox: A Dynamical Model of Disease Spread

    I'm considering a dynamical model of the scenario of a disease spreading across the population, modelling the number of cases, and there's a mathematical puzzle which I'd like to solve. It's kinda different from the S-I-R model, and its also a crude model. First, we consider two numbers, NT...
  18. archaic

    B Something like an inverse Zeno's paradox

    The paradox I am referring to is that which can be resolved by considering the fact that ##\sum_{k=0}^\infty1/2^k=1##. However, before one can travel half of the distance to be travelled, he has to travel half of that half, and half of that half ... Moreover, to say that one can travel by halves...
  19. KipIngram

    I Struggling with a special relativity "paradox"

    Ok, I hope someone can help me see how to sort this out. Alice has a full-frame (no rolling shutter) video camera that records exactly 30 frames per second. It's mounted to a telescope looking far out into space. Bob is out there in space with a digital clock that reads out to the millisecond...
  20. G

    I Vsauce's video on the Banach-Tarski paradox

    A question to Vsauce's famous video about the Banach-Tarski paradox at 10:09: Can you really construct the hyper-webster like that? If you choose the order like that, you'll never get any words containing other letters than "A". Shouldn't you choose an order like A, ... , Z, AA, ..., AZ...
  21. e2m2a

    I The Simultaneity Paradox: Investigating Net Rotation of a Balanced Beam

    Suppose there is a beam balanced on a fulcrum at its center of mass. One observer at rest with respect to the beam sees two lightning bolts strike the ends of the beam simultaneously, such that there is no net rotation of the beam. However, a moving inertial observer sees one bolt strike one...
  22. A

    I How does the N signify the indistinguishability in the Gibbs Paradox?

    Gibbs introduced the N! to then make S extensive. He then attributed the N! to the particles being indistinguishable. How does the N! signify the indistinguishability?
  23. S

    Question regarding the three polarizer paradox

    Summary: Does the three polarizer paradox work with other materials? Alright, so this is going to sound like a dumb question, but if you were to do the three polarizer experiment but replace the polarizers with a another material, could the different material produce a similar effect to that...
  24. J

    I Speed of Light Paradox: Neutron Star Rotation Rate

    Sorry if this is a stupid question but I couldn't find an answer anywhere. According to 2 scientific papers, the neutron star PSR J1748-2446ad has a rotation rate of 716Hz, which equates to a linear surface speed of 0.24c. What if this star was originally rotating, let's say, 5 times (or more)...
  25. Colonel Travis

    B Is a Universe Without Parallel Universes Possible in the Multiverse Theory?

    Does any parallel universe theory include the concept that in at least one of the parallel universes, there is no option for there being parallel universes? If so, how could that unique universe not kill the entire theory?
  26. VVS2000

    Friction Paradox: Unlocking the Mystery of Constant Speed Motion

    I was reading this book on mechanics by derek raine and came up on something called friction paraddox. Suppose a block is is moving with constant speed and the external force is balanced by friction. We know friction causes heat dissipation and the external force supplies some energy so as to...
  27. P

    I How Does Quantum Field Theory Address Zeno's Paradox of Touch?

    How is the contact, or the interaction of electrons, if, according to Zeno's paradox, the distance between objects is divided into infinite points?
  28. Buckethead

    B Relativity: Twin Paradox - Is Age Determinable?

    (I swore to myself I would never ask a relativity question again...oh well) I don't know why I can't find anything about this in a search so I guess I'll just have to ask. Is a twin that takes off to Mars to stay, younger than a stay at home twin or is it ambiguous? I would think that this...
  29. SamRoss

    I Why Is the Green Observer Always the Bent One in the Twin Paradox?

    I feel a little guilty writing this post because I'm sure there are people here who are tired of answering questions about the twin paradox, hence the FAQ post on the subject, but there's something which is still nagging me. First I have a question about the FAQ post itself. Toward the bottom of...
  30. T

    B Banach-Tarski Paradox: Exploring the Ultimate Magic Trick

    Hi! Does anyone think Banach-Tarski's paradox needs reworking? I first came across it in a video by Vsauce. I've been told that things might be reworked as to avoid the paradox, just as set theory was fixed so as to avoid Russell's paradox. How to make sense of a smallest unit of space is what...
  31. A

    I Special Relativity: Train in Tunnel Paradox Solved

    Hello, I was wondering if anyone could set up and solve a classic train in a tunnel paradox from special relativity with unique values for multiple observers including time space diagrams. Thanks
  32. S

    B Is the "Information Paradox" close to getting resolved?

    Is the "Information Paradox", close to getting resolved?
  33. fluidistic

    A Non interacting Fermions satisfy the Pauli exclusion principle

    This question is more a question I'd ask in a chat rather than formally on paper/forum. If we take the free electron model, the electrons are considered as non interacting. It is essentially a 1 particle problem where the potential is constant through space. The electrons are not perturbed at...
  34. S

    B Bohr's duality paradox 100 years later?

    Bohr declared it the duality paradox. It works. But a paradox in science is an unresolved problem. Are we any closer to resolving that problem 100 years after Bohr's declaration, or has the physics community just grown numb to it?
  35. Molloy

    Thermosphere temperature paradox?

    This quote from Wikipedia says that temperatures in the Thermosphere can reach 2,500 C during the daytime but "despite the high temperature, an observer or object will experience cold temperatures". "The highly diluted gas in this layer can reach 2,500 °C (4,530 °F) during the day. Despite the...
  36. Papo1111

    B Is the Twin Paradox Really a Paradox?

    Thanks. This made a lot of things clear to me. But there's one last thing that I want to check: Twins paradox is not a paradox, right? It says that one twin goes to space at near light speed and the other stays back on Earth. Then the one in space returns like f.eg. after 30 years. The twin...
  37. G

    Request about experiments on the linear-motion Faraday paradox

    The Faraday paradox is a very curious example in the topic of relative motion. An experiment demonstrating the curious results is shown in the video below: This has made me curious about the linear version of the Faraday paradox. A conductor placed atop a magnet, both at rest in one scenario...
  38. N

    Relativity Paradox: Solving for Different Observers in the Cloud and Ship

    I'm trying to solve this problem but I get a different answer depending on which observer I solve it for. For the observer in the cloud, the parallel light has traveled 2.294cs, but this is only 0.23cs in front of the ship. 0.23 cs is only 0.086cs in the perspective of the ship due to length...
  39. A

    I Help - pixels per inch paradox

    Hello, I could some help. I've reached some sort of paradox. Ultimately I'm trying to calculate the number of pixels per inch, given a pixel size of 5177 nm and extended at a distance of .7inch (.0178 meters) (A) (60 arcsecs * 0.0178 meters)/206268 = 5177nm pixel per arcmin (B) 5177 * 60 =...
  40. A

    I Paradox: Rocket ship moving in a circle

    Say there is a circular fence that has a diameter of 10 meters, and a rocket ship that is normally 20 meters goes very quickly so that its relativistic length is 1m from the position of an observer standing at rest with relation to the fence. The rocket ship starts to go in a circle inside the...
  41. J

    I Extended Twin Paradox: Explaining Time Lapse and Symmetry Principle

    Suppose an observer (O) sees a traveler (T1) pass by at time t=0, moving a speed 3c/5. Five years later (according to O), T1 returns. If we assume that T1 traveled at 3c/5 for half the journey and instantaneously reversed direction, returning at the same speed, we can calculate that T1 aged only...
  42. S

    I Information Paradox in Black Holes and BSM

    If they could solve the information loss paradox in black hole https://en.wikipedia.org/wiki/Black_hole_information_paradox What other related problems it could solve in Beyond Standard Models or unsolved quantum questions, etc.? If the LHC could no longer detect new particles, could beyond...
  43. m4r35n357

    I Solve General Relativity "Paradox" w/ Automatic Diff. ODE Solver

    After making a couple of comments on this StackExchange question, and pointing yet again to this article, a thought occurred to me. I have been working on an Automatic Differentiation based ODE solver and equation analyzer, mentioned in this thread. Why not use it to solve equation (7) in the...
  44. X

    I Understanding the Relative Velocity Paradox

    Hi! I'm an utter novice at physics, so please bear with me if I ask a foolish question. I just learned that velocities don't purely add: 2m/s + 2m/s does not equal 4m/s, but something like 3.9999999...9 m/s, and so on. Something to do with the upper limit of c. Logic makes me assume that this...
  45. M

    Quantum Zeno Effect and Evolution Operator Properties

    Homework Statement Let ##U_t = e^{-iHt/\hbar}## be the evolution operator associated with the Hamiltonian ##H##, and let ##P=\vert\phi\rangle\langle \phi\vert## be the projector on some normalized state vector ##\vert \phi\rangle##. Show that $$\underbrace{PU_{t/n}P\dots PU_{t/n}}_{n\text{...
  46. TheQuestionGuy14

    B Is the Andromeda Paradox accepted in physics?

    https://en.m.wikipedia.org/wiki/Rietdijk%E2%80%93Putnam_argument Is the Andromeda Paradox accepted in physics? It seems to be based on the concept of relative simultaneity, but it seems quiet nonsensical. Wouldn't every observer seeing a different time period violate causality?
  47. E

    B Why would non-locality solve the time paradox in dcqe?

    I've been trying to work out exactly what part of the experiment I'm fundamentally not getting. The experiment basically says that no information is being sent back in time because the coincidence counters are needed to isolate the signal photons and expose the interference pattern. But the...
  48. P

    B Black Hole Paradox: Exploring Theories

    Just a question: Can anybody give any information regarding the black hole paradox? There are so many theories behind it. Which one should we believe? Just a general question.
  49. J

    A Hardy's Paradox and lorentz invariant realist interpretation

    Does Hardy's paradox show that all realist interpretations cannot be made lorentz invariant? Or is it just realist hidden variable theories?
  50. Sorcerer

    I Understand Twin Paradox, Leading Clocks Lag & Doppler Effect

    I have an obvious understanding failure here, so hopefully someone can help me clear this up. Thanks for reading this obnoxious drivel.Leading clocks lag So, if two clocks are fixed to a the ends of a barn, and they are set off with light pulses from the midpoint, in the frame of the barn the...
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